T-SQL or PowerShell to move bak files older than 2 days to another location
This Powershell example will find all .bak files older than two days in the c:\backup folder and move them to \shared\archive shared drive.

Get-ChildItem c:\backup\*.bak |where {$_.LastWritetime -lt (get-date).adddays(-2)} |move-item -Destination \\shared\archive


Note you cannot run PowerShell commands directly in SSMS. Try it in a SQL Server Agent job step, or just in a PowerShell command window. Should work fine in either.