2010 to 2013 Migration

Hi!

We have a single Exchange 2010 Server installed on win 2008 R2 which we need to migrate to a virtual Exchange 2013 on win 2012 Datacenter server. What is the proper way to do that and what is the hardware and memory requirements for 400 Users on a virtual server. Each mailbox will have maximum of 2GB size except 3 or 4 users who will have 10 to 15 GB limitations.

Thanks.