I have just purchased a laptop (windows11) and want to reinstall newest version of Mach3.  Just getting back into your world!

Firstly, Mach3 software requirements are listed here;
https://www.machsupport.com/software/mach3/

Assuming your PC and motion controller meet the requirements then…

Make a secure backup of your existing Mach3 folder.
Download the latest version of Mach3 from here;
https://www.machsupport.com/downloads-updates/mach3-downloads/
Install over the top of your existing Mach3 version.
Only if necessary, copy from your backup folder to the new Mach3 folder…
Mach1Lic.dat
Any special screen sets or Macros
<your profile> .xml
Etc.

Tweakie.