If you don't need the waveform and just want the measurements, then you could just tell the scope to do it and return those values. You don't mention which model of scope you're using but the Tek scopes I use have these measurement functions. Look for a VI called something like Conf Meas. It's a lot faster to return a couple of scalars than an entire waveform. If you need the entire waveform anyway, you can use the function Extract Single Tone Information. This is on the Analyze>Waveform Measurements palette and is not available in the base version of LabVIEW. This function uses a waveform datatype as input and you're probably getting a 1D array from the scope, use the Build Waveform function to and wire the 1D array to the Y input and your scope's sample time to the dt input.
The input is a wavefrom datatype. The waveform datatype is a cluster with dt, t0, and Y. That's why I said use the Build Waveform function with the Y data you get back from the scope. Or it you look inside the Extract Single Tone VI, you will see that dt and Y are removed from the waveform and passed to other functions. You can make your own VI from this that requires Y and dt.