If you have acquired the .nsp update file for your backup, follow these steps using standard homebrew tools: Option 1: Using Goldleaf (SD Card Install)
Nintendo Switch Title: PAYDAY 2 Developer: Overkill Software (Starbreeze) Publisher: 505 Games Initial Release Date: February 27, 2018 File Format: NSP (Nintendo Submission Package) / NSZ (Compressed variant) PAYDAY 2 Switch NSP UPDATE