The password for the Upgrade is in the email with the link to the Upgrade download.
You must install an Upgrade over an existing installed module. The error message says that the install cannot find the Payables module to Upgrade in \Softrak\Payables. The previous version would have been found in \Softrak\APWIN. You should be able to browse to that location in the install.
Are you trying to install the Upgrade to Payables (taking Payables from 8.1 to 9.2A), or the recently released Service Pack to Payables (which updates Payables 9.2A to fix issues discovered in the original release)?
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Andrew Bates