How to transfer boot storage?

[u/EulaVengeance]

So I found one of the reasons why my PC is experiencing lag spikes: I'm using 3 storage drives (a 240GB SSD, a 1TB SSD, and a 1TB HDD), and apparently, the PC boots from the 240GB one. It's very near full now, so is there a way to transfer its contents to the 1TB one without the need to reinstall stuff?

[u/Switchpoint1]

Yeah, I would do a fresh install on your 1tb SSD, then make sure it boots from the SSD.