I read that a straight current carrying conductor generates magnetic field around it in form of concentric circles. If so, where would be the poles of this field.
Actually you can't talk about poles here. The pole model assumes two hypothetical opposite poles as north(+) and south (-) analogous to electric charges just for an analogy to the Coulomb's law for the H-field of magnets. This model doesn't explain magnetism produced by electric currents.
Ampere hypothesized that all magnetic fields are due to electric current loops. In this model developed by Ampere, the elementary magnetic dipole that makes up all magnets is a sufficiently small Amperian loop of current. The magnetic field produced by currents in this way, also called as B-field, neither starts nor ends but forms closed curves hence there is no starting point or end point, as you read that straight current carrying conductor generates magnetic field around it in the form of concentric circles, hence no pole concept to bring.
For example, when a steady current passes through a solenoid, what you see as "poles" are the two ends of the solenoid, as if the field starts from one and ends on the other. But, inside the solenoid the field is continuous and therefore the "field lines" are closed curves. Inside a bar magnet, the "field lines" continue from south to north and forms closed curves.
Some distance away!
Honestly. See Rod Nave's hyperphysics, and take a look at this picture:
This is like a very short solenoid, the North pole is on the left, the South pole is on the right. Your straight current-carrying conductor is merely one section of the loop. You might think you don't have a loop, but you do. It might not be a neat and tidy loop, but it is a loop, because your current-carrying conductor is part of a circuit.