Open Opera, goto the URL opera://about and take note of the "profile" and "cache" paths. Then, close Opera.
Then, delete everything in Opera's profile and in the cache path.
Then, in Chrome, using the profile you want to import from, goto the URL chrome://version/ and take note of the profile path. Then, close Chrome.
Then, copy everything in Chrome's profile folder to Opera's profile folder.
Then, move the "Cache" folder in Opera's profile folder to Opera's cache path.
For example:
Copy all files and folders in "C:\Users\yourusername\AppData\Local\Google\Chrome\User Data\Default" to "C:\Users\yourusername\AppData\Roaming\Opera Software\Opera Stable".
Then, move the "C:\Users\yourusername\AppData\Roaming\Opera Software\Opera Stable\Cache" folder to "C:\Users\yourusername\AppData\Local\Opera Software\Opera Stable" so that its location is "C:\Users\yourusername\AppData\Local\Opera Software\Opera Stable\Cache".
Then, just start Opera and don't import anything.