Latin help, please- declining mille passus

[Okie]

we are in Latin Alive! chp 28. for ex. 1 dd is I always had dd decline nouns and conjugate verbs (as well as syllabication). Dd is having trouble with mille passus, milia passuum (sorry, don't know how to insert macrons). Passus and passuum aren't the problem, but rather the mille, milia. We're probably overlooking it, but still...

HELP!

[latinteach]

we are in Latin Alive! chp 28. for ex. 1 dd is I always had dd decline nouns and conjugate verbs (as well as syllabication). Dd is having trouble with mille passus, milia passuum (sorry, don't know how to insert macrons). Passus and passuum aren't the problem, but rather the mille, milia. We're probably overlooking it, but still...

HELP!

From Allen and Greenough's Latin Grammar

"134. Of the Cardinals, only ūnus, duo, trēs, the hundreds above one hundred, and mīlle when used as a noun are declinable.

...

d. mIlle, a thousand, is in the singular an indeclinable adjective.
In the plural it is used as a neuter noun, and is declined like the plural of sedIle (section 69): mīlia, mīlium, mīlibus, etc."

So...

nom. mīlia
gen. mīlium
dat. mīlibus
acc. mīlia
dat. mīlibus