how to change batteries on magic mouse

I don't think you can on the Magic Mouse 2 with rechargeable batteries.

On the MM1 there's a little switch that slides towards the end that releases the battery cover.

Oh sheesh, I guess I am really supposed to post a link to the Apple document about this since apparently it does not suffice to say that all you need to do is slide a switch to change the batteries. ◔_◔

Change Magic Mouse batteries - https://support.apple.com/guide/mac-help/change-magic-mouse-batteries-mh29201/mac

Basically if you can see a switch you can change batteries and if you don't then you can't. As I said earlier, that's because with the MM1 you can and with the MM2 you can't.