.Lj3850 sounds like a compiler generated label in the resulting assembler code. It may be the compiler's fault. Try to compile your project with code optimization turned off (-O- command line parameter).
This solution is good?
1) search Lj3890 inside *.o. My result is adm_ceval.o
2) I rename one variabile name onto Lj3894
3) Lazarus->Compiler>Cleanup and Build (again)
No. If the compiler (or more precisely linker) tells you that such a symbol is missing this more often than not points to a bug of the compiler which most of the time occurs in context of optimizations. So as
korba812 said, disable optimizations and try again (if that works, then it's some optimization bug). You can also check whether the development version of FPC shows this behaviour as well. If it's indeed a bug then it would be great if you'd reduce your code to only the buggy part and report a bug
here.