Working in a charity shop (paid or unpaid) is not a hospitality sector job. Hospitality is stuff like hotel work, restaurant/bar work, travel and tourism and suchlike.
If it said customer service work then volunteering in a charity shop may be relevant (although if they state a specific time period they probably mean that period as full time equivalent i.e. the equivalent to having worked a year in a full time job in that role/function; it's probably unlikely you'll have done that amount of volunteering anyway).
Of course they do just say they "prefer" that so if you can link your experiences in the charity shop to what they are looking for in someone from a hospitality background then you can certainly apply (but I wouldn't recommend holding your breath too much for it!).