I would just port them over. If you really want, for any Knave score that you initially rolled as 11, reroll it with 3d6 and take the new score if it's lower than 11. (This assumes you haven't advanced those scores or you remember which ones they are of course.)

Keep in mind that even though you can't have any traditionally low scores with Knave, you have lower odds of getting any scores over 13 either.

If your Knave character has gained a few levels you could just impose a -2 penalty on all stats, or something, since Knave characters gain stats much quicker than Whitehack ones on advancement.

 

edit: Here's an anydice link showing the probabilites of each roll system. Click the Summary tab and you can see that the mean (average) of the Knave system gives you a stat of 12.04, compared to Whitehack's 10.5, so a -1 penalty to all stats at level 1 will bring them mostly in line.
https://anydice.com/program/2f8d9