Windows phones have all its contacts backed up on Microsoft account. Even the contacts stored on sim won't be appearing unless you import them to microsoft account. Unlike android , There are some restrictions to move contacts to other phones. You will have to log on to outlook.com in order to manage your contacts. Here i'm gonna tell you how to get all your contacts in windows phone moved onto an android device.
Log in to outlook.com(with the Microsoft account on your phone)
There on the people tab, you will find all the contacts on your phone. if you have recently added some contacts, long tap Microsoft account on your phone to get an option to sync. And after this step, the newly added ones will get on to Outlook.com(people)
Now you should download a file containing those contacts (.csv file format),
Then It can be imported to your Google account. Now all your contacts on Windows phone is currently available on your google account. Setting up the same google account and syncing will bring those contacts to your phone.
