Money mule schemes work by advertising jobs either in emails or
on web sites. Once you've accepted the job you'll be asked by your
new employer to receive some money into your bank account. You are
then asked to get Ukash with this money, keeping a 'commission' for
yourself and then to send the voucher codes to your new
employer.
Beware that ACCEPTING THESE FUNDS INTO YOUR BANK ACCOUNT IS A
CRIMINAL OFFENCE under anti money laundering laws and you will lose
all of the money received.