The question is not super effective. You are being asked about prior basis. If you are doing a correct backdoor Roth, you have no prior basis because you converted it previously.
You must convert the earnings as well, and pay income tax on them, otherwise it is not a proper "backdoor Roth." If you have a balance of $7014, of which $7000 is non-deductible basis and $14 is tax-free growth, and you only convert $7000, the pro-rata rule comes into play, and you end up not doing a real backdoor Roth and things get messy. The point is to convert the contribution and the earnings, but generally you want to do them close in time so the earnings are very small.
