First of all, do you have them in order (first, second, third...)?

If yes, then the problem lies in simply brute-forcing the 3 words, which is about 8 billion tries.
This number may look scary, but in fact it's doable even on an average PC in a few days at most.

How exactly did you lose the last words?
If you still have some parts of them left, this will make the brute-forcing process easier by several orders of magnitude.