John Gill Commentary Ezra 8:35

"The children of the captivity, that were come out of exile, offered burnt-offerings unto the God of Israel, twelve bullocks for all Israel, ninety and six rams, seventy and seven lambs, twelve he-goats for a sin-offering: all this was a burnt-offering unto Jehovah." — Ezra 8:35 (ASV)

Also the children of those that had been carried away, which
were come out of the captivity
Namely, those that now came along with Ezra:

offered
burnt offerings unto the God of Israel ;
by way of thankfulness for their deliverance from captivity, and for their safe journey:

twelve bullocks for all Israel :
according to the number of the tribes; and there might be some of every tribe that now came up:

ninety and six rams, seventy and seven lambs ;
these and the bullocks were burnt offerings:

twelve he goats for a sin offering ;
according to the number of the twelve tribes, also to make atonement for sins they had been guilty of:

all this was a burnt offering unto the Lord ;
excepting the twelve he goats, which were a sin offering.