Yo encuentro. This is from the verb "encontrar", which is an irregular verb. It is of a class that is referred to as "stem-chaging" verbs, meaning the "stem" (the part of the verb after one removes the ending of ar, ir, or er) varies when the verb is conjugated.
In this case, the stem is "encontr". This changes by altering the "o" to "ue". This change is appled to the conjugated forms except the first and second person plural. The present tense conjugation is: yo encuentro, tú encuentras, él/ella/usted encuentra, nosotros encontramos, vosotros encontráis, ustedes encuentran.