iPad 7th generation black screen

If the screen does not turn on at all, you are probably experiencing hardware issues. To get these hardware issues fixed, take your iPad to the local Apple Store. If you think that the iPad and is in perfect condition, contact the Apple support team here for help: Apple Support

note: Even if your iPad is in perfect condition your battery could have worn out, so if you contact Apple support and they can’t help, take your iPad to an Apple Store to get the battery fixed/replaced

See this article.

If your iPad won't turn on or is frozen - Apple Support