Im really scare right now, I just found out that my Dad has to go to Vanderbilt for atleast 3 months?

I'm 13 and my Dad is leaving in 2 - 4 weeks to go to a Cancer Treatment place in Tennessee ... I have to stay with my Grandma for 3 months and we can't even communicate very well ... im so scared and I have no idea what to do right now...........He has Lymphoma Cancer.............How do I deal with something like this .... 8th grade starts in a few weeks and I' m scared out of my mind right now.........