... Actually very challenging. Even more so in FS because the "Boomers" are not lending a hand from the KC-135 in terms of extending the drogues or hoses. Boomers are the USAF and other aircrewmen depending on their nationality which are in control of the refueling systems in back of the KC-135.
Anyhow, if you want to try it yourself look for c135fr19.zip right here in the Flightsim libray, and read all instructions.
Flying from LFML Marseille to join up with the tanker at FL 160, made several attempts ... got pretty close, but this Mirage F1 is very much a handful at airspeeds below 300 KIAS.
Landed at the nearest base, LFMO Orange-Caritat.
Including one real KC-135/Mirage 2000N air to air refueling pic at the end.