This KB article explains how to request the RMK Site ID, Site Name and Data Center from the RMK site in SuccessFactors Recruiting Marketing
SAP SuccessFactors Recruiting Marketing
Usually, your Implementation Partner can provide this information.
If they do not have this, create a support incident and specify if you need the information for a Production or Preview RMK site.
KB article 2453404 - Procedure to get RMK site manager access in command center
sf, successfactors, RMK, RMK site, site ID, Site Name, Data Center, dc , KBA , "site details" , LOD-SF-RMK-CC , Command Center , How To