Although your question is incomplete, I believe I know what you want to know.
The suffix used for perfect tenses of verbs is -ed/-d.
However, this only refers to regular verbs: if a regular verb ends in a consonant, you add the suffix -ed such as in work - worked. If a verb ends in a vowel, such as in believe, you just add the suffix -d: believe - believed.
On the other hand, if a verb is irregular, you have to memorize the forms by heart because each irregular verb is different.
