Upgrade from 10.04 to 14.04 ubuntu desktop

I am running 10.04 ubuntu version and since it's out dated now, I want to switch to 14.04. Can I upgrade to 14.04 from 10.04 or do I have to re-install the distribution. Also my ubuntu 10.04 is a 32 bit OS and hence I want 14.04 to be 64-bit.

Some specifications of my current system are:

lscpu
Architecture:          i686
CPU op-mode(s):        32-bit, 64-bit
CPU(s):                2
Thread(s) per core:    1
Core(s) per socket:    2
CPU socket(s):         1
Vendor ID:             GenuineIntel
CPU family:            6
Model:                 23
Stepping:              10
CPU MHz:               2992.621
Virtualization:        VT-x
L1d cache:             32K
L1i cache:             32K
L2 cache:              6144K

Also running this gives

getconf LONG_BIT
32

and

uname -a
Linux Sal 2.6.32-73-generic-pae #141-Ubuntu SMP Tue Mar 10 17:30:23 UTC 2015 **i686** GNU/Linux

I know my machine can support 64 -bit OS.

So how can I upgrade it??

Thanks in advance