I am designing a frequency modulated continuous wave radar sensor module, I want to know as the level of IF signal is low at output, what level of amplification would be required to analyse the output by a microcontroller later.
Gain = Output/Input, so you need an amplifier with a gain of (whatever microcontroller needs)/"low" = a big amount.
In other words, some numbers are needed to determine a useful gain. If you don't want the amplifier to clip, then you have to work out the gain based on the maximum input peak. If you don't mind clipping, then you can use the smallest peak that you expect to see and amplify it to the maximum value acceptable to the microcontroller to set the gain.
Clipping or saturation is undesirable if you are handling an analogue waveform into an ADC that you need to preserve the relative values of the sample. However, if you are only looking for edges for timing purposes, as long as the amplifier doesn't introduce extra edges when it clips, it would be acceptable.