The attorney will receive the I-140 notice; he/she should then fax or scan/email a copy of it to the employer. The USCIS says they try to issue the receipt notices within 10 business days, but most of the time we see it's anywhere from 2 weeks to a month. Especially with the H-1 cap opening, there will be a longer delay in receipt notices.
Your employer is not required to provide you with the receipt number/copies/etc. - it is at their discretion.