Please solve the programming task below using a self-contained code snippet in a markdown code block.

You are given an array of strings words and a string pref.
Return the number of strings in words that contain pref as a prefix.
A prefix of a string s is any leading contiguous substring of s.
 
Please complete the following python code precisely:
```python
class Solution:
    def prefixCount(self, words: List[str], pref: str) -> int:
```