how to disconnect this wiring harness?

[ElmerFudge]

I didn't find this in previous discussions, and couldn't figure out how to post in existing thread, so I'm asking for help. I'm replacing the engine compartment wiring harness with one from a salvage yard. Almost ready to plug it in, but can't figure out how to unclip the firewall interface side connectors.
I need to pull the peripheral connectors (blue and 2 white in the picture) in order to pull the main connector plug through the firewall.
I'm having difficulty finding and/or pressing the lock tabs. Any advice will be greatly helpful.

Thanks, Elmer.

 

[tron67j]

Not sure, but it looks like the white clip on blue plug may slide up, releasing it. What does the side of the new base look like in that area of where the blue plug is located?