What is the new temperature (in degree Celsius) after the sample is transferred to a new container with a volume of 2.65 L and a pressure of 1.26 atm?

You have not mentioned the original temperature, pressure and
volume in your question. That does not allow me to give you an exact answer. Instead, I will
provide an expression in which you can substitute the original values to get the new
temperature.

Let the original temperature be To, the original volume
Vo and the original pressure Po.

Apply the Ideal gas law which
states that P*V = n*R*T, where P is the pressure, V is the volume, n is the amount of the gas in
moles, R is a constant and T is the temperature.

As the amount gas
does not change when it is shifted to the new container, we can write the gas law as: P*V/T = n*R
= constant.

The new values, and the original values can be equated
in the following manner: Po*Vo/To = 1.26*2.65/Tf, where Tf is the new
temperature.

Tf = To*2.65*1.26/Po*Vo

Tf
= (2.65*1.26)*(To/Po*Vo)