How do I convert a percentage(linear) to a dB(logarithmic) value as most of the accuracy values stated in power meter data sheet are in percentage?

You may convert percentage (linear) to dB (logarithmic) by using the following equations:
dB = 10 log(1 + X)
Example X = 1%
Thus,
dB = 10 log(1 + 0.01)
dB = 0.0432