slow moving kitchen sink drain best way to clean-out

[rrose002]

I have little experience in unclogging plumbing and would appreciate some advice on where to start, I have pictures of the back of the sink from inside the cabinet
and a picture of the outside cleanout at least I assume that's a cleanout

 

[CT18]

Clean all that foam out and undo the adapter and try to get the snake down there. I guess you could see if it goes straight up and out roof. You could run the snake down from roof

 

[rrose002]

Ok, thank you, sir I'll give it a go.

 

[Geofd]

Can you show a picture of that disconnected pipe is that a p trap????