@Kunal You could use

var htmlSource = nlapiPrintRecord('PICKINGTICKET', internalId, 'HTML').getValue();

for an existing picking ticket, then use the generated HTML as a starting point or reference for your advanced template. You may need to specify the form number, like this:

nlapiPrintRecord('PICKINGTICKET', internalId, 'HTML', { formnumber: 123 })