Your declaration of sort allows only one possible call: sort()
If you want to pass an array to sort, you must declare it
appropriately:
 public void sort(int[] arrayToSort) {
   ...
 }

Such a call
 sort( stuff [0] )
passes ( stuff [0] ), that is, the zeroth element of stuff,

The error message that you paraphrase refers to a declaration you failed to
show us, that of array1.  (Incidentally, names that reflect implementation,
like "array1", "string3" and the like, should be more descriptive and less
tied to the specifics of their implementation.)

The error message tells you that you tried to pass an 'int' to the method
'sort()'.  Since you say that you passed 'array1[0]' to 'sort()', then
'array1[0]' must be an 'int'.  That means that 'array1' is an 'int []', which
also implies that you cannot have assigned an 'int [] []' to it, despite your
claim otherwise.

The best way to resolve the inconsistencies in your presentation is to provide
a complete code example, literally an "SSCCE"
<http://www.physci.org/codes/sscce.html>
a short, self-contained*, compilable example.

Include with your example a precise description of your expected results and
precisely how the realized results differ.  Literally copy and paste relevant
error messages and other relevant text output.

If circumstances preclude providing an SSCCE, the closer you come to that
ideal the better we're able to comment wisely on your situation.

* Andrew: "self-contained" is a "unit modifier" that precedes the noun
modified, therefore requires a hyphen.  I also discard the term "correct" and
the parentheses because "compilable" subsumes what we're trying to accomplish.
 If the issue is a compiler error, then it's compilable with an expectation
of compiler error; if the issue is run-time, then it's compilable with an
expectation of no compiler error.  IOW, I'm construing "compilable" in the
broadest sense of "ready to submit to the compiler".