Fb_exchange_token parameter not specified

[interactive.uxresear]

Hey,

I have some issue about connecting with Oauth Facebook Graph
I did a login with oAuth that is working well, now I want to get a Page token to do so I initiliazed an Oauth Work flow

I created this endpoint to open graph api login flow

And now I have this endpoint to get page access of the current user (Im in manage_page access)

https://graph.facebook.com/oauth/access_token?grant_type=[fb_exchange_token]&client_id=[client_id]&client_secret=[client_secret]

Can someone help me, my deadline is in 3 days