How do you search c disk for all the files with the extension txt

What Samuria says is quite correct and workable. It's also possible to use a third-party search tool -- I'm a devoted user of Voidtools (Search) Everything tool, which is faster and more capable than built-in Windows search -- to search for *.txt, either on a single drive or some combination of drives.
HTH,
--Ed--

FreeBooter said:

You can't use Dir or any other commands to list only text files with file size 150kb...

Not in a Command prompt, but you can in Powershell. This finds all *.txt files in the current directory or below in the size range 150kb to 300kb.

Code:

Get-ChildItem *.txt -recurse | where  {($_.Length) -gt 150KB} | where {($_.Length) -lt 300KB}

Well, actually you can run Powershell commands in a Command prompt, like this...

Code:

powershell  "Get-ChildItem *.txt -recurse | where  {($_.Length) -gt 150KB} | where {($_.Length) -lt 300KB}"

If you search recursively from the root of the C:\ drive you'll want to supress error messages when trying to access folders you don't have permission for. To do that you should add -erroraction 'silentlycontinue' to your powershell command.

Code:

Get-ChildItem C:\*.txt -recurse -erroraction 'silentlycontinue' | where  {($_.Length) -gt 150KB} | where {($_.Length) -lt 300KB}

Maybe if you explain exactly what you are trying to do we can be of more help. Why do you need to use CMD prompt or RUN box?

Bree, when I run the last example you posted, this is what I get:

Code:

PS C:\Windows\System32\WindowsPowerShell\v1.0>         Get-ChildItem C:\*.txt -recurse -erroraction 'silentlycontinue' |
 where  {($_.Length) -gt 150KB} | where {($_.Length) -lt 300KB}


    Directory:
    C:\Users\ztruk\Documents\AppData\Local\Packages\Microsoft.Windows.Cortana_cw5n1h2txyewy\AC\AppCache\ADAOO2L2\101


Mode                LastWriteTime         Length Name
----                -------------         ------ ----
-a----       10/30/2015   5:07 AM         272448 C__Windows_SystemApps_Microsoft.Windows.Cortana_cw5n1h2txyewy_cache_De
                                                 sktop_2[1].txt


    Directory: C:\Users\ztruk\Documents\AppData\Local\Packages\Microsoft.Windows.Cortana_cw5n1h2txyewy\LocalState\Devic
    eSearchCache


Mode                LastWriteTime         Length Name
----                -------------         ------ ----
-a----        2/15/2016   9:33 AM         226246 SettingsCache.txt


    Directory: C:\Users\ztruk\Documents\AppData\Roaming\Roxio


Mode                LastWriteTime         Length Name
----                -------------         ------ ----
-a----        4/23/2015  11:23 PM         183934 PlasmaLog.txt
Get-ChildItem : Access is denied
At line:1 char:9
+         Get-ChildItem C:\*.txt -recurse -erroraction 'silentlycontinu ...
+         ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
    + CategoryInfo          : NotSpecified: (:) [Get-ChildItem], UnauthorizedAccessException
    + FullyQualifiedErrorId : System.UnauthorizedAccessException,Microsoft.PowerShell.Commands.GetChildItemCommand



PS C:\Windows\System32\WindowsPowerShell\v1.0>
PS C:\Windows\System32\WindowsPowerShell\v1.0>         Last edited by Bree; 1 Hour Ago at 06:19 PM.
At line:1 char:32
+         Last edited by Bree; 1 Hour Ago at 06:19 PM.
+                                ~~~~
Unexpected token 'Hour' in expression or statement.
    + CategoryInfo          : ParserError: (:) [], ParentContainsErrorRecordException
    + FullyQualifiedErrorId : UnexpectedToken

PS C:\Windows\System32\WindowsPowerShell\v1.0>
PS C:\Windows\System32\WindowsPowerShell\v1.0>       My ComputersSystem Spec
My : The term 'My' is not recognized as the name of a cmdlet, function, script file, or operable program. Check the
spelling of the name, or if a path was included, verify that the path is correct and try again.
At line:1 char:7
+       My ComputersSystem Spec
+       ~~
    + CategoryInfo          : ObjectNotFound: (My:String) [], CommandNotFoundException
    + FullyQualifiedErrorId : CommandNotFoundException

PS C:\Windows\System32\WindowsPowerShell\v1.0>     Quote Quote   Multi-Quote This Message
Quote : The term 'Quote' is not recognized as the name of a cmdlet, function, script file, or operable program. Check
the spelling of the name, or if a path was included, verify that the path is correct and try again.
At line:1 char:5
+     Quote Quote   Multi-Quote This Message
+     ~~~~~
    + CategoryInfo          : ObjectNotFound: (Quote:String) [], CommandNotFoundException
    + FullyQualifiedErrorId : CommandNotFoundException

Why am I getting the errors, other than Access Denied, those I understand.

Must have, sorry. Did it again and ran in the Powershell ISE and it worked great.