Can i upload my unfinished tax returns to the cloud to finish? they are on my computer

No ... the 2019 return started on the downloaded version cannot be opened on the online version ... it only works the other way around.  

And if you switch to the Online web version you have to pay again for Online.  You can not apply the Desktop purchase to online.  They are separate things and don't talk or sync to each other.  You would have to get a refund for the Desktop CD/Download program and pay for online separately.

Why would you even want to?    The computer (desktop) version is much more robust and contains features missing in online versions.