I saved a movie to itunes where can I find it now

Open iTunes. Click on the Store tab at the top of the iTunes screen. Go to the dropdown selection box at the left of the screen and choose Movies. In the side bar select Home Videos.

-- Rich

Here's Apple's help bulletin regarding iTunes:

https://support.apple.com/en-us/HT210200

You may need to download iTunes from the internet.

https://www.apple.com/itunes/

-- Rich

Here's another link where you can check whether your Mac is too old (obsolete) to download iTunes:

https://support.apple.com/en-us/HT201624

-- Rich