Answer:
Dear whom it may concern,
I was wondering whether there was a volunteer job going at your place of establishment.
I am currently in (say grade, ect) and my name is (add name). I would absolutely love to volunteer at Heart to Heart. I am extremely ambitious and have a great work ethic; I feel like I would be an amazing asset to your team.
This job is especially important to me as I would love to have a career in healthcare when I am older and because of this I want to build up my resume. Why do I want a career in healthcare? I want a career in healthcare because I want to help people as best as I can. This volunteering job would help me get a boost to my future endeavours.
Thank you.
Yours sincerly ....
(notes: its not 150 words but its gives you a rough idea of what you need to say :), its also not very good but i hope it helps <3333)