What it means
I'm lost. 迷路 means to lose your way, 了 marks the situation as current.
When to use it
Show a map or an address when you say it. If you can add 我要去这里 (I want to go here), you've covered the whole conversation.
Examples
wǒ我mí迷lù路le了，néng能bāng帮wǒ我yī一xià下ma吗？
I'm lost, could you help me?
bù不hǎo好yì意sī思，wǒ我mí迷lù路le了。
Sorry, I'm lost.
wǒ我men们zài在shān山lǐ里mí迷lù路le了。
We got lost in the mountains.
The full set of survival phrases for greetings, dining, shopping, and getting around, each with audio.