What experience is required for going first time at white water rafting or clear creek rafting specially when it comes to Colorado rafting, estes park rafting, denver rafting ?

None whatsoever, just the ability to follow instructions.
Bit of a long way to travel for this activity though ;)

Ps you forgot the helpful link...

If you are going with a guided raft, then you need no experience. If you are going in a group of rafts without a guide in each boat, it would help to have someone experienced at steering the raft and spotting the best line to take.