How to convert sound represented in dB with different reference values ?

There are several methods for characterizing sound.

The underwater sound is represented in dB with different reference values, such as :

    (i)        dB ref 1 µPa    

   (ii)        dB ref Pa2/Hz           

   (iii)       dB ref Pa/√Hz 

   (iv)        dB ref 1 µPa in 1 Hz band

I would be grateful if you could tell me how to convert (through a Matlab code) the sound pressure/Intensity that is given in dB with above references.

For example how to convert 80 dB sound with 1 µPa reference into dB with Pa/√Hz reference and vice-versa.

If there is a Matlab function that can do this, then that would be great.

Regards,

Sunil Tyagi