The word prefix has two syllables. When used as a verb, the stress is no the second syllable. The syllables are pre-fix'.
The first syllable is stressed. The US pronuncation is (PAHST-hu-muss), usually sounding like (PAHS-chew-muss).
Pre
The stress in a prefix used as a noun typically falls on the first syllable.
In the first pronunciation of the verb prefix, the stress is typically on the second syllable. For example, in the word "decrease," the stress is on the syllable "crease."
Footprint is stressed on the first syllable.
Captive is stressed on the first syllable.
The first syllable is stressed.
Lightning is stressed on the first syllable.
In the word "lawyer," the first syllable "law" is stressed.
It is not entirely clear whether you are asking which syllable is stressed or what the first syllable is. The stressed syllable is the first syllable: sev.
Saunter is stressed on the first syllable.
District is stressed on the first syllable.