I'd like to purchase turbotax pro to access my previous returns, but there is no option from my account.

Here's an article that outlines how to access a prior year return:

https://ttlc.intuit.com/questions/4236074-prior-year-return

Here's an article that outlines how to access a prior year return:

https://ttlc.intuit.com/questions/4236074-prior-year-return