It looks like you would purl the stitches off the cable needle instead of knitting them. The F in that instruction is hold the cable needle in front of the work. It makes a cable in the opposite direction of the CB.
There is probably a key somewhere in your pattern that explains the abbreviations, but basically, you’re right.
c= cable
3= number of stitches in the cable
b= back
p= I’m guessing this means purl? but it’s hard to say without seeing a little more of your pattern. If it’s a free pattern, could you post a link?
It looks like you’re working from the mainly purl side of the work. Instead of working the cables from the knit side it has your working the cables from the purl side, so I assume the P in the cable instructions would be a purl. So you would purl the cable stitches on the outer cables and knit the cable stitches when you work the center cable.
Once I figured out what all those abbreviations meant it suddenly all made sense and I was able to knit that cable. Now let’s see if I can incorporate it into a hat pattern that I am designing!