how do I find or change my iCloud pin?

My phone is asking for my phone pin.. which I have, but it is asking me for my iCloud pin.. which for the life of me I cannot get correct. I also have no clue how to change the name on my account or download all the stuff I purchased over the years. I have not used my iPad in a few years and just got an 11 after using an android for a couple of years... so I am returning to apps after a hiatus, but still have my original applexcloud id... having difficulty setting it all up... ie, iCloud pin, DL purchased items(music and apps), Changing my name on the account.... thanks...