If you just need the inventory from the previous LCA, and I would suggest using the inventory rather than the CO2e result, then I think your best bet is to convert that inventory into a spreadsheet that openLCA can import. You can get a template for what that looks like by exporting a process from openLCA to an Excel spreadsheet.
If you need to have the sub-process level information that went into the previous LCA, I don't think there's straightforward way to do that. You would be repeating the above for all those sub-processes and then connecting them in openLCA.