Here's a possible interpretation and correction:
"Si je peux le faire, je le ferai."
This translates to:
"If I can do it, I will do it."
Explanation:
* "des" is incorrect here. It's a contraction of "de les" meaning "of them" and doesn't fit in the context.
* "je peux le fais" is grammatically incorrect. The correct conjugation for "I can do it" in the present tense is "je peux le faire."
* "je le ferai" is the future tense of "I will do it."
Let me know if you had a different phrase in mind!