You'll need at least 9 RCA cables:
You need 1 RCA cable for each speaker channel -- 7 for the main speakers and one for each of the subwoofers. The main speaker RCA cables go between the processor and the amplifiers and all 7 would be approximately the same length, since the two amps would be approximately the same distance from the processor. (3-6 feet, probably) The RCA cables running to the subwoofers will be quite a bit longer and likely would be different lengths, depending on where you put the subs. (15-30 feet, maybe).
Depending on what your input devices are, you might need two RCA cables for each of them, too.
Each speaker should already have two visible external jumpers installed between the HF and LF binding posts -- one jumper between HF and LF on the + side and one between HF and LF on the - side. If the jumpers are missing and you can't easily get replacements, you can use standard speaker wire to connect between the binding posts. Once the jumpers are installed, it doesn't matter if you connect the amplifier to the HF or LF binding posts.
The wires used between the amplifiers and the speakers are not RCA. They're stranded speaker cables. Most people use 16 gauge.
Marantz SR7009/7.1.4/FH+TM/DefTech PM1000/LCR+TM amped