Want to file case to many parties through msme samadhan portal but i dont have purchase order

First of all decide what action can be taken against the default buyers/customers.

The delivery challan in your possession or the copies of the gate passes  also would serve as documentary evidence to maintain your complaint case for recovery.

In the absence of proper (conclusive) evidence your case cannot be proved.

It is better to consult and engage a local prudent lawyer for proper advise and necessary proceedings

Dear Client, in that case, you should file an affidavit with a prescribed format it will also work. If you need that, you can call me then I'll serve it.
Advocate Anurag Bhatt
Allahabad High Court
Mobile 9198889990.