Why do I have a ton of 2k & 4k docs on my Verizon cloud?

[AC Question]

My wife and I are Verizon android users. For an unknown reason on her Cloud, she has a ton of Docs that can't be opened. We even tried emailing them to ourselves to see if a laptop would do it. It says they are of an old format. (Or something to that effect) my daughter watches YouTube on her phone all the time, so concerned that she might be hacked. help!!