How to get the exact same music library on my iphone and ipad?

I have two iphones and an ipad on the same itunes account and can sync everything on its own for each device which is great for apps and such. The problem I'm having is I have a little over 6000 songs on my itunes and I took the time and went through all of it to get ones I really like and ended up with about 500 on my iphone since I use it in the car. How can I get that same music library I put on my phone onto my ipad as well. Do I really have to go through all of those songs again? I know if I sync the two then apps will mess up cause some ipad apps won't go to iphone so either way syncing will make them a mess. Is there a way to just get same music on both? Don't know much about itunes match but if that is the answer does anyone know of a free option since I don't want to pay for 1 year when I will probably do this only one time then go back to manually managing like I do now… Please help and thanks

Added (1). I have I cloud but i'm not sure how to use it other than for backup in case phone needs reset. Do I have to sync everything if I use icloud? I only want same music if possible cause iphone is more of a fun apps play around with kind of device but I have mainly college stuff and photography work on ipad

Sync to iCloud and then log onto iCloud to sync all devices

You can't get icloud? That is supposed to sync everything.literally everything.music, pictures, apps, notes, etc.