Windows 10 20H2 upgradation on Lenovo Thinkpad T510

Hi, I came across this which I add just for interest - it sets the context for your older laptop:
Should I fix my six-year-old laptop or replace it? | Technology | The Guardian

Your laptop has a decent CPU and you have a SSD, albeit somewhat small.
You will need at least 30Gb free on C:

Noting you are running 1709, that begs a number of questions, starting with why you are running such an old build.
Have you disabled Windows Update?
Is your O/S damaged, such that attempting to upgrade may fail?

Every single build of Win 10 can be downloaded (tutorial available).
If you were to upgrade manually by downloading a specific build, you would upgrade to that build if you did not choose to update as part of that process. Thus you could upgrade to any specific build you wanted.

If you upgrade via Windows Update, then you will receive the latest build MS deems compatible with your device. I.e. which build you get depends on MS.

You can upgrade from a given build to any later build you like, provided it is compatible. I.e. you can skip builds.

Recommended: before attempting to upgrade, create a disk image of your current build so that if something should go badly wrong you can always restore your PC to as was. Macrium Reflect (free) is recommended time and again here, as is the routine and regular use of disk imaging. Other such programs exist e.g. by Aomei, Easeus.

Your 510 appears to use Conexant sound hardware.
Recent builds of Win 10 have had issues with this. See articles in the News section where there is a thread per update per build for 20H2 builds and updates.

It is common with older Lenovo's that the fingerprint reader stops working - no driver. See:
FIXED! Driver for fingerprint reader T510 Windows 10? - Thinkpads Forum

BIOS: ensure you have the latest available version. Lenovo System Update can help if that's available for your device.

Drivers- mostly for Win 7, a few Win 8, are here:
Lenovo EOL Portal

You should update to 2004 using the ISO file method if you want to keep all your data, then update to 20H2 using Windows Update. Hopefully it will be offered to you.

20H2 just unlocks a few features in 2004, it`s barely even a update.

You should trim down 1709 as much as possible, remove anything you don`t use or need.

And of course make a backup image with Macrium Reflect before you attempt anything.

Macrium Software | Macrium Reflect Free

Create SSD Backup Image with AOMEI Backupper

Version 20H2 has used only 21.9 GB in my case.

Buy a reasonable HDD to use for disk imaging.
If you have anything that matters on that PC you need to back it up.
If something goes badly wrong, you will have to clean install Win 10 and risk losing everything without a backup.

And use disk imaging... not just a backup of your personal files.

Still wondering why you are on build 1709 and how much free space you have on C:

Note that upgrades can fail. If that happens, it's often next to impossible to diagnose the problem.