Upgrading SQL is a bit outside the scope of this forum. You can do an in-place upgrade between the Express versions, but, you need to make sure that you have taken appropriate database backups in the event that the upgrade were to fail.
What is your need to upgrade? How many clients are you managing, and what products are you using? You're also on ePO 5.1.0. There have been many maintenance releases and hotfixes since 5.1.0. Depending on how many clients you are managing and what products you have, you may be better off with some longer term planning to migrate off of SQL express entirely and on to a SQL server with SQL Standard or Enterprise as SQL Express has some severe locks and limits on how big the database can be, etc.