Application Migration Service - Powershell Module - Returns only 50 records

What is your use case. Could you please brief on the same. I am guessing that the powershell output is enabling pagination which is causing you to see only 50 records. Please check if you are getting a nexttoken in your reponse. Output Pagination with AWS Tools for PowerShell

I havent tested this code, let me know if this works:

# Get the account ID
$account_id = Get-Account

# Get the first page of results
$results = Get-MgnSourceServer -AccountId $account_id -MaxResults 100

# Loop through the results
while ($results.Count -gt 0) {

    # Get the current page of results
    foreach ($source_server in $results) {
        Write-Host $source_server
    }

    # Get the next page of results
    $results = Get-MgnSourceServer -AccountId $account_id -MaxResults 100 -NextToken $results.NextToken
}

You may try out some of the below steps if it works for you:

1. In case of powershell, total number of items to return in the command's output could be controlled by using the parameter -MaxResult <Int32>
2. If your command result returns more than the value defined for MaxResults, then you would need to use the parameter -NextToken to fetch the next set of records.
3. You may also try the AWS CLI describe-source-servers with options like --no-paginate or --max-items
4. You may try the AWS API documentation for DescribeSourceServers with request body maxResults or nextToken Let me know if this helps you.