Firstly, you will need to open a Word session and click open.
Then, click Browse and go to H:\Documents as below.
You will then need to scroll to a file called Normal.dotm and open it.
It is likely that this will show as being in compatibility mode at the top of the screen.
This means that you will need to convert the file from Word 2010 to Word 2019. Got back to File in the banner at the top. Then click info. You will want to click the convert icon which will take you back to the main document.
A config box will pop up to ask you if you want to upgrade. Click OK.
Then save the file back to H:\Documents with the same name. It may ask to replace the existing file, if you wish to keep the existing file then you may want to save it with a different name.
After this, you will want to close all Word sessions down and copy the Normal.dotm to %AppData%\Microsoft\Templates.
Once it has saved in this location, you will be able to use your old Autotext files. Please be aware that this is only for the computer you are using at the time but you can copy the version saved in H:\Documents on any PC you log on to. You should not need to repeat this on the same PC again.