SQL Server MIN and MAX memory setting

Hi,

We are using SQL Server 2016 Ent with SP1 (This is Stand alone server and only One instance not any other applicaitons)

How to set Min and MAX server memroy? There 40-50 DB running on this server 

What happens if i set MIN-256GB and MAX-256?

Please provide your recommendaitons. These are hight transactional DB's.