How do I see the Access Key/Secret Access Key

Access key and secret access key are not visible from the S3 screen.
Check from the IAM screen.
You can also check the secret access key at the time of creation, or check the contents of the CSV file that you can download when you create it.
If you have access to the AWS CLI, you can use the following command to check the access key and secret access key set for a user.

aws configure get aws_access_key_id
aws configure get aws_secret_access_key

To expand on the answer from Riku_Kobayashi - you can retrieve your AccessKey from your IAM user profile in the IAM console, however there is no way to retrieve your SecretKey if you did not save it somewhere at the time you created your AccessKey.

The only option you have here is to create a new AccessKey - you can have up to two active AccessKeys, and you can disable (or leave active) the existing one prior to deleting it if you think it might still be in use, until you are able to replace it with the new AccessKey to avoid impact to applications that might be using it. [1]

Please note, where possible, our best practice is to use temporary credentials [2] rather than long-lived AccessKeys.

[1] https://docs.aws.amazon.com/IAM/latest/UserGuide/id_credentials_access-keys.html [2] https://docs.aws.amazon.com/IAM/latest/UserGuide/best-practices.html#bp-workloads-use-roles