I am working in USA on H1 visa since 1 and half year. and i have travelled earlier to USA three times before this and i was on L1 visa.now i want shift to another company .The new employer is asking me previous L1 visa petitions, which i have lost. what should i do
Let them know about it. They might be asking for L-1 petitions to see how much time you have already spent in US on L-1. You can use the immigration stamp in your passport to get those dates.
How long did you stay outside US after completing your last L-1 trip but before having H-1 filed?