Can i do an exension for my LLC with only one member and how much I need to pay?

What kind of LLC?  Are you a Single Member LLC?  Did you set it up as an S corp?  If not an S corp  it is a disregarded entity and you file it on schedule C in your  personal tax return as self employment.  So you just do the extension for your personal tax return.  

a single-member LLC, that did not elect corporate taxation, is a disregarded entity for federal income tax purposes. it does not file its own tax return. Rather the results are included in you 1040. What you need to do in this case is determine your overall tax liabilty. Pay it on or before 4/15 (some exceptions apply). if you can't file by 4/15  submit an extension Form 4868, but your taxes are still due as noted above.  

An LLC is a legal entity, not a tax identity. If you are the sole owner and never requested to be a corporation, it is part of your tax return, on sch C. Just file your personal extension, the business is part of it.

Otherwise, the tax deadline was Mar 15.

Be sure to make any payments by April 15. You can make Payments online safely. Remember your  Self-employment tax  is included in the amount due. Only the paperwork is extended.  See:

• How do I file an IRS extension (Form 4868) in TurboTax Online?
• Do I need to file an extension for my personal state taxes?
• Do I need to file an extension if I'm getting a refund?