A SSD, as the boot drive, is the least expensive way to increase system performance of a desktop or laptop. It is not as difficult as it may seem to do the upgrade. The best way that I have found is, leave the hard drive disk (HDD) installed as it came from the factory. Install cloning software on it. Connect the SSD to another SATA port on the motherboard or M.2 socket. Run the cloning software. It will ask for the Target Drive and that will be the SSD. Once the HDD has been cloned to the SSD you can go into the BIOS to change the Boot Order to the SSD and reboot. The system should boot to the SSD. Some manufacturer's provide the Migration software and other software to tweak the performance of the SSD once it is installed. The HDD can remain as storage.
If you are upgrading the M.2, SSD, to a larger M.2 you will most likely need a USB to SATA/NVMe adater.
Note: Make certain to have the BIOS set to AHCI. This will allow the SSD to function at peak performance.