Hi Guys. I am a beginner and I need Help!

Actually I need to trigger a micro pump attached to the quad (actually for collecting air samples at various altitudes )

How do I accomplish that?
what flight controller do I use ?
How many channels maybe necessary?
Can I use the auxillary channels and a simple circuit to do that ?

Please suggest ideas
thanks in advance   

assuming your pump is driven by a brushed dc motor

just attach a brushed motor esc to the aux channel and assign
a switch on your tx to put it on

there are a myriad other ways - but above is the simplest.

Does it mean I need auxiliary channels on my flight controller .

Suppose I have a kk control board which has 5 channels (4 + 1 for self level )
and I have a receiver with 8 channels how do I connect it
can I make use of the the remaining 3 channels to trigger the pump on and off

or do I need a  better flight controller which itself has more connections
Please help

ok so you have a kk board and from receiver
you plug how many channels 4-5 ?
so if a six channel receiver - then you still
have a channel slot free on the receiver.

plug the esc into a spare slot in the receiver
and assign a switch to switch on and off

this is not the most elegant way but it is easy to implement