Hi there @mrwnphs2 !
Unfortunately, Canvas does not currently provide you with a way to bulk change the item-type of existing items in your course. I think the best way to go about this would be to copy and paste all of the information from the assignment using 'control A', and pasting it onto the page. To save you time, I'd recommend having the page open in one tab and the assignment open in the other so it's just a matter of switching tabs back and fourth and not scrolling through different areas of your course one after the other.
Even though this isn't the news you were hoping to hear, I still hope this helps in some way!
Best,
Noah