Divide table raw into chunks

I have a table with too long entries with 1s and 0s. For example I have
table :

| Sent id.| BoW. ||---------|----------|| 1 | 10100101 ||
2 | 00011110 || 3 | 10101111 |

I want to create new table which will divide column BoW. entries into some
arbitrary length and assigns chunk number.

| Sent id.| Chunk No. | BoW. ||---------|-----------|------|| 1
| 1 | 1010 || 1 | 2 | 0101 || 2 | 1
| 0001 || 2 | 2 | 1110 || 3 | 1 | 1010 ||
3 | 2 | 1111 |

I am beginner, tried to search in documentation, but without success. Maybe
something like this, but with proper function:

select b.sent_id, chunk, substring(bow from (chunk - 1) * 4 + 1 for
4)from (select b.sent_id, generate_series(1, 1 + floor(length(bow) - 1
/ 4) ) as chunk
from bow1 b
) b;

I have 4623 Sent ids (sentences) and each is 10,000 characters long. I want
to divide them into 32-40 character long chunks.