"I thought about a new job."
Translation:Ik dacht aan een nieuwe baan.
I hope someone else comes along and provides a corroboration or correction of this, but as I understand it, the word order of a prepositional phrase is always (tricky statement) "preposition-object." So "aan een nieuwe baan" remains "aan een nieuwe baan."
Where it gets tricky for me (and maybe for you) is when there is a separable verb. The verb's prefix is (or looks identical to) a preposition, and that prefix would get moved from the root verb to the far side of the verb's object. If the verb in this sentence had been "aandenken," then "Ik dacht een nieuwe baan aan" would have been correct, I believe. However, looking at a few online dictionaries, I can't find a verb "aandenken." (There's a noun het aandenken, which appears to be equivalent to English's (borrowed from French) "souvenir" -- an object that brings a memory to mind -- but no such verb.)
There is, however, a verb "nadenken," and I believe this sentence with "nadenken" would be "Ik dacht een nieuwe baan na."
Having written all that, I'll add that I would welcome any help for Chenmoxin and me.