How create validations within the create invoice page in the supplier portal?

Summary:

We want to know how to put the following validation inside the Invoice number field:
be no less than 3 alphanumeric characters, no special characters or spaces should be allowed.

and That the ERP system does not allow invoices to be saved when they are not sent (send button), generating an alert message to the supplier that the invoice cannot be saved until it is sent.

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