From my extensive experience in this area (true crime podcasts lol), if your hitman is either quoting a reasonable price or offering a payment plan, they’re a cop.
And the ones asking for payment up front will enjoy the free money. What, were you going to get a receipt for that?
You can get a SAS USB external enclosure but they're in the $100 range, probably not worth it for 3TB.
For internal use, you can get a used PCIe SAS Host Bus Adapter fairly cheap BUT you need to do some research. Before you buy one you should confirm that there is a driver for the OS that you are using and that it is supported on your processor/socket/chipset. These cards are server hardware - many of them are not supported by Windows and/or are not compatible with consumer motherboards & CPUs.