The number listed in this thread WHO Transfers clearances from SC to JPAS? (866 prefix) still worked for me when I last called in a couple months ago. They’ll ask for your SSN over the phone.
If it’s been 2 years then a new background investigation will likely be needed. I know i waited this long for DIA adjudication and by that time the company lost the contract.
The address is fine, except you don’t need the words “electronic requests.” In the letter request you need to sign and date a Title 28 U.S.C. 1746 jurat (“I declare under penalty of perjury. . . .”) at the bottom of the request. SC is a database record. It doesn’t include the background investigation reports. For the reports you will need to submit a PA request to the agency that did the investigation.