How do you port fabric mods to another version of minecraft?

If this is your mod or you want to edit the code see this: https://fabricmc.net/wiki/tutorial:migratemappings.

If not then open the jar file in 7zip or WinRar or Archive Manager or some sort of archive program.

Next edit fabric.mod.json and change the line saying "minecraft": "<a minecraft version>" to "minecraft": "*".

If there is no line, do nothing.

Even if you do this it is very unlikely it will work unless you edit the code.