How much alcohol do you have to consume ..

In order to have it in your system . It's been 9 months obviously pregnant until I started back drinking. Never was a drinker b4 but my husband and I go out and I casually drink . I had 1 drink and felt so guilty about it Bc I breastfeed my baby . Nonetheless that's all I need . But i took those testing strips and it came out negative I was still ify about those so I pumped more and tested it and again negative .

So just curious how much do you have to drink to need to test your breast milk .