Skype includes a feature that allows you to find specific text in a chat.
This FAQ will walk you through the steps of doing so.
Locate Specific Text in a Skype Chat
One way to do so is to use the Find field. Click in the message field, press CTRL + F to display the search field, then type the phrase you’re looking for:

You can also use the Find command by typing the following code into the chat field and pressing Enter:
/find text
