Hi cieja,
there's no need to be worried. If you are able to get the 11th version, it allows to open the 10th version's files too. So, get HFSSv11 and open the files made with v10. You can re-save them in HFSSv11 and simulate again.
Bye.
Added after 4 minutes:
PS--> You may find some slight difference in solution in v9.2 and v11 (if both file's versios are correctly set) but it depends on the way the convergence algorithm is implemented in HFSS11 respect to v9.2 and on the way you set the sweep type, solution frequency and mesh characteristics.