It sounds like your boat's floor may have been modified. Those strips of wood screwed down may have been a way of making the floor "permanent". Look closely before you unscrew them, though.
Also, you said 4 sections. My Zodiac, which is only 3.1 metres long, has 5 sections. Has someone already made new panels for yours?
To remove a standard plywood floor. deflate the tubes sufficiently to remove the side pieces ("stringers") then reach down the side and pull up on the joint nearest to the middle of the boat. Those two boards should come up to make a "tent" and you can remove them, then remove the others.
Replacing the boards is a skill requiring "the knack". It's basically the same as taking them out, but in the opposite direction. Four hot tips:
- When putting the boards in, put the bow and stern sections in first.
- Support the bow with the fuel tank or something of similar size.
- When you put the last 2 sections of floor in, make a "tent" then push down on it. (I stand on mine) until all of the floor is almost flat.
- Put an oar shaft under the side of the boat to provide a hard level guide that you can push the floor down against while you're manoeuvring the stringers into place. (The 2nd stringer is always a bit easier than the 1st.)