That's also what several here have already said.
And, the process is easy (fairly easy), and quick (less than an hour should do it, assuming you haven't piled on lots of apps already
)
Plug your iPhone into your Mac (or Windows PC), run iTunes.
Click on your iPhone icon. click the backup button, just to make sure that iTunes does that.
Click restore.
Wait until that process is complete, then choose to restore your backup. iTunes will ask you about that at the appropriate time.
I think there is an app that you have to run on your android phone to set up the transfer of your messages. Follow the instructions for that app, whatever it is.
Should work, and is the same tip that you should have asked about before you first setup your new iPhone.
If you move between very different OSes, then you should expect that you will have to jump through a few hoops to get from one to the other. This is one of those "hoops"...
Take your time for discovery, start over, and do it right this time
I bet that the shop where you got your new iPhone would have also helped you quickly (and correctly) with this, rather than you trying to discover how to fix your set up after the fact through random internet questions.