How to use baseline correction function for single mass intensity values?

Hello, I have an imaging dataset in the form of multiple text files. Each text file represents the intensity values for a specific mass for all the pixels. In each text file there are some header lines and then 3 columns comprising the coordinates and intensity values(x,y, intensity) for that specific mass. Now I want to perform baseline correction (using function msbackadj and other pre-processing steps on this file. But I always get an error, which I guess is due to the manner in which the data has been organized. Can anyone help me here? A sample file is attached.