V/W for watakushi

V for watakushi
V and w are interchangeable in Japanese and represented by wa わ in hiragana.

Wakakushi wa - means I am

So to say " I am Smith"
Watakushi wa Sumisu desu.
desu is is/am/are and is always written at the end of the sentence. The sentence formation is subject object and verb. (sov) unlike English where it is SVO(subject verb object).

So to say your name
just say Watakushi wa _______________ desu.
In Japanese, there is no way you can write sm(two consonants together). So a dummy sound (u) is introduced. So Smi - Sumi and there is no th and hence it is replaced by su.
So Smith is Sumisu. Also since our names are foreign to Japanese, there should always be written using katakana instead of hiragana.
スミス - Sumisu
 - Jakuson(Jackson)