Assuming no other legal change, you’d be doing the same apportionment math we have historically applied under The Reapportionment Act of 1929

The Reapportionment Act of 1929 capped the number of representatives at 435 (the size previously established by the Apportionment Act of 1911), where it has remained except for a temporary increase to 437 members upon the 1959 admission of Alaska and Hawaii into the Union.

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Since 1941, seats in the House have been apportioned among the states according to the method of equal proportions.

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In this method, as a first step, each of the 50 states is given its one guaranteed seat in the House of Representatives, leaving 385 seats to be assigned. The remaining seats are allocated one at a time, to the state with the highest average district population, to bring its district population down.

Consider the reapportionment following the 2010 U.S. census: after every state is given one seat:

1. The largest value of A1 corresponds to the largest state, California, which is allocated seat 51.
2. The 52nd seat goes to Texas, the 2nd largest state, because its A1 priority value is larger than the An of any other state.
3. The 53rd seat goes back to California because its A2 priority value is larger than the An of any other state.
4. The 54th seat goes to New York because its A1 priority value is larger than the An of any other state at this point.

This process continues until all remaining seats are assigned. Each time a state is assigned a seat, n is incremented by 1, causing its priority value to be reduced.

Of course, I would simply repeal the The Permanent Apportionment Act of 1929 as part of the legislation that incorporated these territories as official US states. It’s a bad law. It creates bizarre political incentives for both the US Census and the function of the lower chamber. It incentivizes gerrymandering of what is engineered as a scarce political resource. And it facilitates a bunch of downwind bad behaviors in the states that have mimicked it, to date.