Hmm I don’t think the data migration over projects is supported in any way. There are hacky ways where you fetch all the vectors and then upsert them into a new index, but its messy imo.
What I would hope that would be one day possible is project independent collections where collections created would not be linked to a specific project. At the time I don’t think this is so.
If you have the Free index full (thats around 100k vectors?) the easiest and fastest way (not the cheapest) is to just run the process again and fill the new index.
Long story short. No there is sadly no clean or easy way to migrate your data from one index to another over different projects.
A comment regarding a similar topic (not the same issue):
Best of luck