How to do the FFT and denoise using dB 10 in Matlab

I want to do FFT and denoise using dB10 using matlab then plot and save all the data to an appropriate txt file later on for the 6th column of the prcdata after dividing by 1.16E6 I seen the code for FFT in matlab but tried that but it wasn't working my code is

%% clear [filename, pathname] = uigetfile('*.raw;*.prc', 'Pick raw or processed data file'); N=str2double(filename(5:6)); % load processed file fid = fopen([pathname filename],'r','b'); A= fread(fid,inf,'*single')'; prcdata=reshape(A,N,[])'; plot((1:size(prcdata,1))./1.16E6, prcdata (:,6))%divides the x axis by %the frequency 1.16E6 and selects the channel 6 from the PRC data %plots the data to a graph title(strrep(filename,'_','-')) fclose(fid); %%