How can we get momentum from time & momentum from force?

there is no such direct conversion but if u are mentioning the conversion of rate of change of momentum with time to force, then for such conversions, we should always remember the second law of motion:

 

The force applied on a body is directly proportional to the rate of change of momentum.

i.e.

F = dP/dt

 

where we have taken the proportionality constant as 1