Press WinKey + R to open the Run dialog box.
Type this path into the text box:
%userprofile%\AppData\Roaming\Microsoft\Signatures
Click OK
There are 3 files (an .htm, .rtf, and .txt ) and 1 Folder for each signature you created.
Press Ctrl+A to Select All
Press Ctrl+C to Copy
Insert a USB/Thumbdrive and Navigate to it.
Press Ctrl+V to Paste the signature files to the removable media
Insert the USB Drive in your new PC and reverse the process.
Copy from the USB Drive, Paste to %userprofile%\AppData\Roaming\Microsoft\Signatures on your new PC.