whats the best mode for the 3pk?? pcm? fm? or hrs alsowere is the cheapest place? please and thank you for your help

i am new to the 3pk so don't know a great deal, but i do know that hrs is the go but only if you are using digital servo's.
pcm is for if you are using analog servo's, both pcm & hrs are fail safe compatable.
so if you are unsure about what servos to use i would suggest going for a pcm receiver.

ok can u use sanwa didgital servo and a duratrax 8t pro with hrs mode?

Your best bet is HRS, and yes sanwa digital servo work with HRS. Digital servos also work with PCM.

"duratrax 8t pro" what is this?

its a esc it has fet capabilities do airtronics servo's use fet?

mmm, nope not sanwa, ko servos do but not many if anyone is using fet.

Keep in mind that you`ll need the particular receiver to allow the mode to work....
ie: to run HRS you`ll need the HRS receiver with digital servos
.....to run PCM you`ll need the PCM receiver but theres no need for the digital servos......same again if you run a PPM receiver.
If youre running a Spektrum module, you`ll only be able to run it in PPM mode, unless of course you`ve managed to get one of the NEW HRS Spektrum sets.
Cheers