Hi, I'm sorry if this is the wrong way to request this, I'm new to forums in general-- I would like the Steam games/hidden games in my collection to be removed, please. Thank you!

You should be able to filter your collection down to hidden Steam games and then perform a bulk delete action by selecting any or all items and clicking on the Edit Selected button.

On your collection page:

Steam games: Filters button -> All Platforms -> select Steam
Hidden games: Filters button -> Hidden - All Games -> Select games hidden

Bulk Edit options: After you've got everything filtered -> Select All (top left of collection screen) -> Edit Selected -> Delete