I am missing 3 months of banking input 2018 JULY AUGUST and SEPTEMBER so I cannot reconcile..how can I fix this

If you are missing 3 months of banking transactions, you have more problems than recons. The P&L and the balance sheet can not be correct either.

Relying on banking downloads to make your entries is a misconception intuit advertising promotes. You should be making the entries as they occur, and then you just match the download if and when you get it, or do a manual reconcile from a statement - 5 min max monthly. Making entries as they occur is the only way to have an accurate current company financial file.

log into your bank site, and look for a download that uses any of the following file types, that download can be imported into QB (.qbo, .qfx, .ofx). TO import, if I remember right, top right corner under update QBO is the link to import that manually downloaded file.

Go to the bank's website and download a CSV file, which QBO lets you import.  The date range should be from the beginning until the day before the first transaction in For Review, assuming you started the business in July. The file should be good as is, but you can open the file in Excel to make sure there are 3 columns: date, description and amount, withdrawals as negative. 2 columns for date also works.  Then upload the file into For Review:

https://quickbooks.intuit.com/community/Banking-and-bank-feeds/How-to-import-bank-transactions-using...