I-140 approved. Unpaid vacation days for a month

Can I take 1 month unpaid vacation days in US? My I-140 is approved. H1b got expired on July 31,2018 and extension is in process with USCIS. Will it be illegal? Thanks for answering the question in advance.

You have to have a tangible reasons for taking vacation while on H1 in USA. If not, it may be reviewed as a potential BENCH period mitigation. Please make sure that you have a legal reason to take unpaid vacation. But its legal to take unpaid vacation with a good reason.