This is obviously an unanswerable question. We can imagine an unlimited number of possible ways you could encode long numbers into those strings. Just given the string, there's no way to know.
For an obvious example, imagine if you see "4","3","2". That could obviously encode 432, but it could equally obvious encode 234. There is absolutely no way to know which of those two is correct, if either.
If it helps, it does appear to be nearly certain that each of those strings contains 16 bytes of data encoded in base64. Here's the 16-byte data for the three strings you supplied converted into hexadecimal:
lJsFziTUF4LtFzww7d2tVw== -> 94 9b 05 ce 24 d4 17 82 ed 17 3c 30 ed dd ad 57
E4NEi092gWbppbpNR0JUAw== -> 13 83 44 8b 4f 76 81 66 e9 a5 ba 4d 47 42 54 03
+j+hnQx9Wl83MWeM92tyZA== -> fa 3f a1 9d 0c 7d 5a 5f 37 31 67 8c f7 6b 72 64