Read 61.159
§ 61.159 Aeronautical experience: Airplane category rating.
(a) Except as provided in paragraphs (b), (c), and (d) of this section, a person who is applying for an airline transport pilot certificate with an airplane category and class rating must have at least 1,500 hours of total time as a pilot that includes at least:
(1) 500 hours of cross-country flight time.
(2) 100 hours of night flight time.
(3) 75 hours of instrument flight time, in actual or simulated instrument conditions...
(4) 250 hours of flight time in an airplane as a pilot in command ...
(c) A commercial pilot may credit the following second-in-command flight time or flight-engineer flight time toward the 1,500 hours of total time as a pilot required by paragraph (a) of this section:
(1) Second-in-command time, provided the time is acquired in an airplane—
(i) Required to have more than one pilot flight crewmember by the airplane's flight manual, type certificate, or the regulations under which the flight is being conducted;
I'd question if you're ready for the ATP if you can't find a reg.