Install a new SSD but keep all the files and everything
You need to make a complete duplicate ("clone") of your existing internal SSD module onto the new SSD.
You can do this with Disk Utility, but the third-party apps  SuperDuper! and Carbon Copy Cloner are actually better at it.

However, the real problem is having both SSDs attached at the same time to make the transfer. You either need to buy a USB enclosure for one of them, or you need to have an additional USB drive to copy the clone to as an intermediary. You also need to have MacOS on this USB drive, because you'll need to boot up to it. 

(Having a standard USB drive may be more use to you in the long-run,; or you may already have one.) 

First step is to copy the clone onto the USB drive. You can either make the entire disk a clone, or copy the clone as a disk image (file) onto the USB.

Next, you need to install the new SSD in your Mac so you can copy the clone back onto it, but of course you need to be booted to another volume in order to run the cloning app! 

Boot to the USB drive, and then run the cloning software in the other direction.