In this case, the MEX-FCO flight is AZ677 which I can use flightaware.com to check in for more details and in some cases get a flightplan(only for flights to/from/within US territories)
For flight planning, simbrief.com and fpltoif.com work hand in hand in that the latter is used to decode the flight plan made from simbrief. I hope that you’re successful with this flight :)