In place Upgrade Win 10 to a previous build # 4561 to 2965 ?

There are two kinds of installations: Legacy - MBR or UEFI- GPT. Your MB is able to accept both.
Legacy - MBR is the old style and UEFI- GPT is the modern style.

Legacy - MBR normally has 3 partitions: System, C and Recover
UEFI- GPT normally has 4 partitions: EFI, MSR, C and Recover

Let's see what you have.
Please post a whole window Disk Manager image of ALL your drives. Don't forget to expand the columns so we can read them. How to Post a Screenshot of Disk Management
If you have a MiniTool or AOMEI Partition use it instead or Windows disk manager.

Your Windows drive is Legacy- MBR and don't have the System partition.

As Win 11 require the drive to be UEFI-GPT (can also be tweaked) we can make the new MX500 a UEFI-GPT, If you agree with it.

Don't worried, I'll give you detailed instructions.

Attach the new MX500 to a SATA 600 port and to a power supply socket.
Detach all other drives but not the current main drive
Boot normally into Win 10

To prepare the new drive.
Open a CMD window as administrator and type: (you can copy one command line and paste to the CMD window. Then do the same for the next command)

reagentc /disable (Very important. This will disable the recovery environment on the current drive)

diskpart
list disk (it will list all drives. Identify the new MX500 drive number)
select disk n (replace n by the new MX500 drive number obtained with list disk)
clean
convert gpt
create part EFI size=100
format quick FS=fat32 label=EFI
assign letter=W
create part MSR size=16
exit (to exit diskpart)
On the new MX500 drive you now have an empty EFI FAT32 100M partition (W) and a RAW MSR 16M partition.

Launch Macrium Reflect
select the current drive as source to clone
select the MX500 drive as target

drag and drop the Windows partition to the target.
Don't select to clone the Recovery partition
Execute the Macrium Reflect


It's not ready yet. The drive won't boot. There are more steps to be done.
Post a Disk Manager image of the Current drive and the MX500 so I can see the results.

Trapper said:

Thank you Megahertz, that is very helpful!
I have printed it out so I can refer to it when I come to do it. I now have the new SSD and the adapter so will install it later today.
I used to use dos at work decades ago.

Okay. a couple of dumb questions:
When you say, Execute Macrium Reflect, I guess there will be some sort of tick box or enter to be actioned?
Will having FAT32 format for the new drive and NTFS for everything else make any difference, I am not questioning your instructions just wondering why.

The only thing that is FAT32 is the 100MB EFI partition that was created on the new drive with Diskpart.

Trapper said:

Thank you Megahertz, that is very helpful!
I have printed it out so I can refer to it when I come to do it. I now have the new SSD and the adapter so will install it later today.
I used to use dos at work decades ago.

Okay. a couple of dumb questions:
When you say, Execute Macrium Reflect, I guess there will be some sort of tick box or enter to be actioned?
Will having FAT32 format for the new drive and NTFS for everything else make any difference, I am not questioning your instructions just wondering why.

On Macrium Reflect you will start with the source drive (Current) on top and target (MX500) on bottom.
At this point the target (MX500) will have a EFI and a MSR partition created with diskpart. You then drag and drop the Windows partition from the source to the unallocated space on the target. Then press next till done.