Hi hun, it all depends on your height, weight etc. I have heard 125/150cc is roughly 1 size, so I think you would be a good ‘C’ cup.
Best think to do is search for 300cc in the forum and see if you can find a thread with someone with similar sizes.
Also I googled 34b 410cc implants (my stats) into google and it brings up other really helpful forums.
Have you seen a surgeon yet?
xxx