Search software

If you want to search a specified application, you can use "pkg search" command. For example:

# pkg search lsof
lsof-4.90.b,8                  Lists information about open files (similar to fstat(1))
p5-Unix-Lsof-0.0.5_2           Unix::Lsof -- a wrapper to the Unix lsof utility

If you want to know the software's path in the ports tree, you can use -o option:

# pkg search -o lsof
sysutils/lsof                  Lists information about open files (similar to fstat(1))
sysutils/p5-Unix-Lsof          Unix::Lsof -- a wrapper to the Unix lsof utility

In case the Ports Collection is already installed, you can employ whereis command:

# whereis lsof
lsof: /usr/local/sbin/lsof /usr/local/man/man8/lsof.8.gz /usr/ports/sysutils/lsof

Another tricky method is using "echo" command:

# echo /usr/ports/*/*lsof*
/usr/ports/distfiles/lsof_4.90B.freebsd.tar.bz2 /usr/ports/sysutils/lsof

Reference:
Finding Software.