Transferring Spark files from individual account to Teams, maintaining source files

EDIT: Just realized this is in the wrong forum, but don't see an option to move it. My apologies!

I've been trying to get ahold of support but <insert whining and complaining here> no one appears to be available.

We just opened a Teams account that includes a couple of All Apps licenses. We have an old individual account for an employee who no longer works here; she has several Spark projects that we'd like to migrate to Teams. When her files are downloaded locally, they save as a jpeg with none of the source files. In speaking with the sales person while setting up our Teams account, he said that if we uploaded the jpegs to Teams, the source files would be there. I found this hard to believe, so he transferred me to a tech ... except no one answered the transfer, I was on hold for an hour, and then was disconnected by their phone system. Chat has also proved to be zero help, as no agent seems to be available to answer my question.

Does anyone have experience with this? How do we transfer Spark files from an individual account to Teams when the users are different, without losing the source data?

Thank you for any help you can give.