How to associate a PFX certificate from different identity (Windows-7) to upgraded computer (Windows-10) with new identity?

User upgraded to Windows-10 from Windows-7 created logon user identities are different from original. Encrypted data files were copied to new computer, but unable to access/open encrypted files. Installed .PFX and .CER objects from old PC to new one using certlm.msc. Still no joy! Assume the issue is different identities. Old identity is XXX-SSD while new identity is MySSD.  CER and PFX objects installed from flash drive.

Reviewing CertLM the certificates appear in following:
                CERTIFICATE           -                      Issued To             [Comments]
 Personal            -                                      MySSD                  [new identity]
Trusted Root Certification                              XXX-SSD                    [prior identity]
Intermediate Certification Authorities      XXX-SSD                    [prior identity]
Trusted People                                        MySSD                  [new identity]
Other People                                               MySSD                  [new identity]
Homegroup Machine Certificates  -            XXX-SURFACE
                                                            XXX-SSD-PC
How do I associate the prior PFX with identity XXX-SSD to new identity MySSD?