Copy VB.Net 2013 program to VB.net 2015

I have a VB.Net Winforms program what was written using VB.Net 2013 for one of my clients.  Now I need to create a new, very similar program for a new client and it appears that VB.Net 2015 is the latest version.  I need to keep the 2013 version so I can support my older client but I must provide my new client with not only the new program but also all of the source code and a copy of VB.Net.  So I need to develop the new program in version 2015.

In the past I have had no problems making a copy of a 2013 program with a new name but how do I copy a 2013 version so it opens in VB.Net 2015?

Thanks,
Charlie