How do we interpret frequency from fft command in matlab?
The output of the fft function will go from 0 Hz to fs/2, then -fs/2 to almost 0.  If you ignore the 2nd half (for purely real signals), the following works well:

For n samples at a sampling rate of fs, you can create a frequency axis, f with the following formula:

f = (0:n-1)/n*fs

This gives you freqs from fs/2 to almost fs, but if you overlook that...

The other option is to use the fftshift command on the fft output and revise the formula

f = (0:n-1)/n*fs-fs/2