Searching for a Purpose

I have spent the last 18 years raising my children and now with the last one leaving for college, I am feeling like I have no purpose. My days are very long. My husband and I plan to travel so I am not looking for a full time job but I need something to fill my time that matters. I don’t know where to start and to be honest I don’t even know what I would like to do anymore. Any direction is greatly appreciated.