Octopus Overlords

Bought a new SSD to replace the old steam HDD after upgrading to Windows 10. What program should I use to copy over the file/partition?

G-parted, but you need to create a boot USB stick first. https://gparted.org/liveusb.php

Rather than messing around with ‘freemium’ commercial software that typically omits important features by design, I'd suggest using a reliable FOSS alternative such as Clonezilla.

Keep in mind though, being FOSS means the UI will likely seem somewhat confusing and significantly less user-friendly than most ‘freemium’ commercial software. So I'd suggest watching the video below to familiarise yourself with how to properly use Clonezilla to clone and restore any system: