Monterey was the last OS that could open an iPhoto Library in Photos. (iPhoto was replaced over 10 years ago!) But the pictures are safe. So, you have two alternatives:
(1) In Photos you can use File>Import to load the pictures from the iPhoto Library into your Photos Library-- you should get them all in good shape. But if you had the pictures organized in events, you will lose that organization.
(2) You can use the trusted 3rd party app PowerPhotos ($40) to convert the Library to Photos and preserve the organization, turning iPhoto Events into Photos Albums. The app is worth the cost if you do lots with pictures in Photos (it's open on my Mac all the time.) But in any case, the trial version will do the conversion for free!
Let us know if this works for you…