I would first filter out the high-frequency noise, most likely with a lowpass (rather than a bandpass) filter. The designfilt function is a good choice. Before you design your filter, use the fft (link) function to determine where the noise spectrum and the signal spectrum are so you can design the filter correctly.
A ‘peak’ is what you define it to be. Depending on what you want to do, use the max and min functions, or the findpeaks function on your signal to find the positive peak and on the negative of your signal to find the negative peak. See the documentation for these functions to determine the best choice for your data.
