Here are various methods you can pick from to convert audio to WAV:
Drag the file from File Explorer to the Reaper timeline. Go to File > Render. Type in a new filename if desired. Click “Browse”, choose “Browse for directory”, choose where to save, then click OK. At the “Output format” drop-down, select “WAV”. Click “Render 1 file”. When done, Reaper reports “Finished in…” within the “Render status” area.
In Adobe Media Encoder (video below)
Drag the file from File Explorer (or from Finder, if on a Mac), to the queue area of Media Encoder. Under the format column, collapse the drop-down menu (triangle on the left, under the filename) and select “Waveform Audio”. Under the “Output file” column, click on the blue text to choose a location for your converted file (and type a new filename name if you like), then click “Save”. Press the green play icon in the top right of the queue area. When finished, Media Encoder reports “Done” in the status column.
Open the file in iTunes. Go to iTunes > Preferences > General. Click “Import Settings”. For the “Import Using” dropdown, choose “WAV Encoder”, and click OK. The next step depends on your version of iTunes: Either right-click the file within iTunes and choose “Create WAV version”, or select the file within iTunes and go to File > Convert > Create WAV version. When iTunes has done this, a new file appears: Right-click this file, and choose “Reveal in Finder” to show the location of the file.