Symbols are written and read from left to right, from highest to lowest.'3475' look like in Roman numerals MMMCDLXXV.
MMMCDLXXV = 3475
If you mean in Roman numerals then in today's modern notation of Roman numerals it is now 3475 = MMMCDLXXV but the ancient Romans probably notated them quite differently.
The Roman numerals are XLV.
18 in roman numerals looks like XVIII
20 in Roman numerals is XX.
300 would be represented by 'CCC' in roman numerals.
MCMLXXXIX
DCLXVI
D1X
MCMLXXXV
MMDCCCLXXXVI
MMI
XLVI