If I didn't know any better, I'd think that you're considering cloning the old drive to the new. Don't do it. It's better to back up all your data on the old drive (use an external backup HDD for this), then remove the old SSD. Install the new one and reload Win10 (or whatever it is you're using for an OS). You'll then want to reload your applications onto the new drive, along with the data you want to keep. Afterwards, if you want to use your old SSD as an additional drive, plug it in, delete all the partitions in it, repartition/reformat it, and off you go.