Hi @d.rajkhowa02, welcome to our community!
I use this in my context, I put this piece of code on my collection Pre-Request Scritps.
pm.sendRequest({
url: YourURL
method: 'POST',
header: {
'content-type': 'application/json'
},
body: {
mode: 'raw',
raw: JSON.stringify({ YOUR PARAM TO CREATE THE TOKEN IF NEED IT })
}
}, (err, res) => pm.collectionVariables.set("TOKEN", res.json().accessToken));
Then on collection Authorization I insert the variable TOKEN and change the Type to Bearer Token. That will help on your problem.