Via the SCCM Console, the Deployment ID for a deployment is not visible by default. To enable this go into the Monitoring workspace. Right click the menu bar and choose Deployment ID from the list.
The Deployment ID's are now visible.
Via PowerShell you can use the Get-CMDeployment cmdlet. Entering Get-CMDeployment will return all deployments. You can filter via a specifc ID using the command:
Get-CMDeployment -DeploymentID <deploymentID>