What version of iMovie for 10.12.6?

I believe that iMovie 10.1.7 is the version for Sierra.

If you have or ever have had iMovie 10 on your computer you can follow this procedure to get the highest iMovie version compatible with your operating system:

To update/redownload iMovie 10, drag your iMovie 10 app from the Applications folder into the trash, but do not empty the

trash. (You can skip that step if you had iMovie 10 on your computer before, but deleted it.) Sign in to the app store and open your purchases folder by clicking on your name at the bottom of the app store side bar. You will see

your purchases displayed, including iMovie 10. Redownload/update iMovie from there. If not successful, drag your present iMovie app out of the trash (if you moved it there) and return it to the Applications folder.

-- Rich

If you never had iMovie 10 on your computer before, then you will not be able to get it unless you can upgrade your operating system to Mojave 10.14.6, or to Catalina. Upgrading to Catalina would make incompatible all 32bit apps that may be on your computer.

Here are the requirements for upgrading to Mojave:

https://support.apple.com/en-us/HT210190

-- Rich

Yes, you can use iMovie 10.1.8 if you had installed it before. If you deleted it for some reason, you can still get it back using the procedure that I described in an earlier response.

You can keep iMovie 9 as well and use it simultaneously with iMovie 10 if you want. iMovie 9 probably won't work very well on Sierra. You might want to open iMovie 10 and do a File/Update Projects and Events to update your iMovie 9 projects into iMovie 10 projects. You can still access the updated projects from iMovie 9 as well.

-- Rich

what if you have not downloaded imovie before?